D&C 119

As the Church was to continue to grow throughout the world, the Lord revealed -

"...this shall be the beginning of the tithing of my people.
4 And after that, those who have thus been tithed shall pay one-tenth of all their interest annually; and this shall be a standing law unto them forever, for my holy priesthood, saith the Lord." (Doctrine and Covenants Section 119:3 - 4)

I believe it would have been very difficult with the growth of the Church to administer the united order with the law of consecration and stewardship with different world governments and monetary systems. Even though the law of tithing may be considered as a schoolmaster preparatory for the saints to abide the law of the Celestial Kingdom, for some it may be just as demanding. The law of tithing was a more uniform law that would allow obedience by members at varying stages of gospel maturity and allow more uniform administration. With this law, the saints were warned -

"...if my people observe not this law, to keep it holy, and by this law sanctify the land of Zion unto me, that my statutes and my judgments may be kept thereon, that it may be most holy, behold, verily I say unto you, it shall not be a land of Zion unto you." (Doctrine and Covenants Section 119:6)

Elder Melvin J. Ballard said -

"Do we not hope and expect to have an inheritance in the celestial kingdom, even upon this earth in its redeemed and sanctified state? [D&C 88:25–26; 130:9.] What are the terms under which we may obtain that inheritance? The law of tithing is the law of inheritance. It leads to it. No man may hope or expect to have an inheritance on this celestial globe who has failed to pay his tithing. By the payment of his honest tithing he is establishing a right and a title to this inheritance, and he cannot secure it upon any other terms but by complying with this and other just requirements; and this is one of the very essential things." (In Conference Report, Oct. 1929, p. 51.)

Obedience to the law of tithing is a requirement to attend the temple. This only makes sense for how can one covenant to obey the law of consecration without obedience to this lesser law? With the growth of the Church the Lord commanded -

"...this shall be an ensample unto all the stakes of Zion." (Doctrine and Covenants Section 119:7)

President Joseph F. Smith wrote -

"By this principle (tithing) the loyalty of the people of this Church shall be put to the test. By this principle it shall be known who is for the kingdom of God and who is against it. By this principle it shall be seen whose hearts are set on doing the will of God and keeping His commandments, thereby sanctifying the land of Zion unto God, and who are opposed to this principle and have cut themselves off from the blessings of Zion. There is a great deal of importance connected with this principle, for by it it shall be known whether we are faithful or unfaithful." (Gospel Doctrine, p. 225.)